The present invention relates generally to a tube or reservoir which provides a source of clean air for injection into a multi-dose medicament vial prior to withdrawing medicament from the vial for injection into a patient. The invention also relates to a method for loading sterile air into the barrel of a syringe prior to use of the syringe to withdraw medicament from a multi-dose vial.
Liquid medication which is to be injected by needle is often sold in multi-dose containers. In some cases (e.g., insulin), as many as 50 or 60 doses or shots are contained in a single vial. The vials are fitted with a rubber diaphragm, and when a dose is to be administered, the needle of a syringe is pushed through the rubber membrane and the proper amount of liquid medicament is withdrawn for injection into the patient.
Since the vial is airtight, withdrawal of liquid medicament creates a partial vacuum inside the vial, and, after a few doses have been withdrawn, the vacuum becomes enough of a factor to make it difficult to withdraw any further doses. To compensate for this, the standard practice, each time a dose is to be administered, is to inject a quantity of air into the vial first, and then withdraw the medication. As described by Sorensen et al in Basic Nursing, page 949 et seq. (W. B. Saunders Company, Philadelphia, 1979), the standard procedure includes the following steps:
1. Cleanse the stopper of the vial with alcohol or Betadine. PA1 2. Draw into the syringe an amount of atmospheric air about equal in volume to the dose to be withdrawn from the vial. PA1 3. Push the syringe needle through the stopper of the vial, and inject air into the vial. Then withdraw the amount of medication needed. PA1 4. Proceed with injection of the patient.
A source of potential problems in the above standard procedure is that, if the atmospheric air should be contaminated, the contamination is incorporated in the dose of medication and is injected through the skin (normally the body's first line of defense against infection). Pathogens in the atmospheric air are thus introduced directly into the body tissues or blood, where they can cause serious infections. The problem is aggravated if the liquid medication (e.g., NPH insulin) contains suspended solids and must be shaken before the dose is withdrawn from the vial, and shaking is a common practice even when not necessary. In any case, shaking causes the contaminated air to be thoroughly mixed with the medicament. The problem is especially aggravated after 30 or 40 shots of contaminated air have been injected into the vial.
It is an object of the present invention to provide a device and a method for overcoming the above-mentioned problems associated with the injection of atmospheric air into medicament vials.
It is a further object of the invention to provide a specially designed medicament injection adjunct for furnishing the air to be injected into medicament vials.
It is a still further object of the invention to provide a sequence of method steps resulting in loading a medical syringe with sterile air and using such air to obtain a dose of medication for parenteral administration to patients.
Other objects and advantages will become apparent as the specification proceeds.